This invention relates to a method of manufacturing a so-called "pill-box" shaped paper container which is of a dual construction comprising an inner body and an outer body, the container being separated into a container body and its cover.
Such a pill-box shaped paper container is provided for accommodating a material which should be intercepted from light or sealed completely. Typical is a container for photographic film. In general, the container body and the cover thereof are separately manufactured.
However, this manufacturing method is disadvantageous in that it requires a number of manufacturing steps and the work is relatively complicated. This results in an increase of the container manufacturing cost. Also, in such prior art containers there is play between the body and the cover of the container and therefore it is impossible to completely seal a material therein.
In order to eliminate the above-described drawbacks, a method of manufacturing a pill-box shaped paper container has been proposed by Japanese Patent Application Laid-Open No. 148383/1977 in which a box is formed by surrounding a preformed inner packaging body with an outer packaging body blank sheet having parallel perforation lines in the form of a belt in such a manner that the outer packaging body is in close contact with the outside of the inner packaging body. That is, in this prior art method, the container body and the cover are formed as one box, and when the box is used, the cover is formed by removing the belt-shaped perforated portion of the box. This method is improved in manufacturing cost and sealing efficiency compared with the above-described method in which the container body and the cover are separately manufactured.
However, the method proposed by the aforementioned Japanese Patent Application Laid-Open No. 148383/1977 is still disadvantageous in the following areas: It is necessary to provide at least a gap corresponding to the belt-shaped perforated part between the inner packaging body and the outer packaging body. If the panel board of a part of the box, which has the gap, namely, the top panel board is depressed inwardly, then it is readily curved. Accordingly, in the formation of the box, it is difficult to completely coat the top panel board with adhesive. Even if the top panel board is completely coated with adhesive, it is readily deformed if depressed during handling process such as conveying.
When the container manufacturing according to the method is used, it is necessary to peel the belt-shaped perforated part off the outer packaging body, and during this peeling operation the boundary portion between the container body and the cover may be torn. Thus, the container itself presents a problem as to its sealing characteristics.